There is today an increasing demand from passengers to be able to communicate through mobile phones and other handheld terminals when travelling on public transportation vehicles, such as trains, ferries and busses, and also to be able to get access to the Internet with laptops, PDAs etc. However, vehicles of this type are made of metal, and even the windows are often covered with a metal film. Further, vehicles often move between different coverage areas. Thus, direct communication between terminal antennas within the vehicles and externally located antennas is difficult to obtain.
To this end, such vehicles are often provided with an external antenna connected to a data communication router within the carriage, which in turn is connected to an internal local area network (LAN). Hence, the communication between the passengers' terminals and the operator antennas outside the vehicle, and corresponding wide area networks (WANs), occurs through the data communication router. This has been found to be an efficient way of providing e.g. Internet access on-board public transportation vehicles. Such mobile access router solutions are e.g. commercially available from the applicant of the present application, Icomera AB, of Gothenburg, Sweden.
However, today's systems are not entirely satisfactory. In order to provide continuous access, the data communication router typically need to include a plurality of modems, and each modem often needs access to a plurality of subscriber identity modules (SIMs), which makes the communication unit rather large and costly. Further, it may still be difficult to obtain a cost-efficient data communication at all times. In particular this is a problem for vehicles passing country borders, since there is typically different operators handling the WANs in different countries, and roaming between different operators, or even between different WANs belonging to the same operator, is normally very costly. As cross-border travelling is ever increasing, it is nowadays not unusual that the same train crosses up to four country borders on a single journey, and busses and ferries often cross even more borders.
Another drawback with today's systems is that there is a frequent need for upgrading of the systems, requiring update or exchange of modems and SIMs, which in today's systems is rather costly.
Still another problem associated with the present solutions is that even though it is sometimes possible to use a common antenna for several modems, this impairs the quality and efficiency of the transmission, and consequently it is often necessary to have at least one antenna, and possibly even two or more, dedicated to each modem. However, installation and maintenance of antennas is rather costly, and the overall costs increases significantly with every new antenna that is needed.
There is therefore a need for an improved vehicle communication system which provides better capacity and/or lowers the overall costs of installing and maintaining the system.